C#でのAES暗号化　ECBモードとCBCモード

Crypt.cs

using System.IO;
using System.Collections;
using System.Security.Cryptography;

public class Crypt
{
    private const string AesIV = @"8863d67c62113fb8";
    private const string AesKey = @"2eeee02d3dc3ef6c";

	public string EnCrypt( string text )
	{
		
		RijndaelManaged aes = new RijndaelManaged();
		aes.BlockSize = 128;
		aes.KeySize = 128;
		aes.Padding = PaddingMode.Zeros;
		aes.Mode = CipherMode.ECB;
//		aes.Mode = CipherMode.CBC;      // CBCモードを利用する場合は設定をこちらに

		aes.Key = System.Text.Encoding.UTF8.GetBytes( AesKey );
		
		// CBCモードを利用する場合はIVの設定を行う
//		aes.IV = System.Text.Encoding.UTF8.GetBytes( AesIV );

		ICryptoTransform encrypt = aes.CreateEncryptor();
		MemoryStream memoryStream = new MemoryStream();
		CryptoStream cryptStream = new CryptoStream( memoryStream, encrypt, CryptoStreamMode.Write );

		byte[] text_bytes = System.Text.Encoding.UTF8.GetBytes( text );

		cryptStream.Write( text_bytes, 0, text_bytes.Length );
		cryptStream.FlushFinalBlock();

		byte[] encrypted = memoryStream.ToArray();

		Debug.Log( "byte :" + encrypted[0] );
		return ( System.Convert.ToBase64String( encrypted ) );
	}

	public string Decrypt( string cryptText )
	{
		RijndaelManaged aes = new RijndaelManaged();
		aes.BlockSize = 128;
		aes.KeySize = 128;
		aes.Padding = PaddingMode.Zeros;
		aes.Mode = CipherMode.ECB;
//		aes.Mode = CipherMode.CBC;  // CBCモードを利用する場合は設定をこちらに

		aes.Key = System.Text.Encoding.UTF8.GetBytes( AesKey );
		
		// CBCモードを利用する場合はIVの設定を行う
//		aes.IV = System.Text.Encoding.UTF8.GetBytes( AesIV );

		ICryptoTransform decryptor = aes.CreateDecryptor();

		byte[] encrypted = System.Convert.FromBase64String( cryptText );
		byte[] planeText = new byte[encrypted.Length];

		MemoryStream memoryStream = new MemoryStream( encrypted );
		CryptoStream cryptStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);

		cryptStream.Read(planeText, 0, planeText.Length);

		return ( System.Text.Encoding.UTF8.GetString( planeText ) );
	}
}